Water supply apparatus

ABSTRACT

A water supply apparatus is configured to meet energy-saving demands by controlling a pump so that the rotational speed of the pump is lowered while keeping a constant flow rate. The water supply apparatus includes a pump for pressurizing and delivering water, a frequency converter for supplying electric power to the pump to operate the pump at a variable rotational speed, a discharge-side pressure sensor for detecting a pressure at a discharge side of the pump, and a controller ( 15 ) for controlling the rotational speed of the pump. The controller ( 15 ) stores a plurality of control head curves (B, C 1 , C 2 , C 3 ) representing different relationships between flow rates (Q) and heads (H), and controls the rotational speed of the pump based on an alternatively selected one of the control head curves (B, C 1 , C 2 , C 3 ).

TECHNICAL FIELD

The present invention relates to a water supply apparatus for supplyingwater such as tap water to collective housing or a building using apump.

BACKGROUND ART

As an apparatus installed in collective housing or a building forsupplying water to each of water supply ends, there has been a watersupply apparatus. FIG. 1 shows a typical example of such water supplyapparatus. The water supply apparatus includes two pumps 1 combined withrespective motors M for pressurizing and delivering water, and inverters(frequency converters) 2 for supplying electric power to the motors Mfor driving the respective pumps 1. The water supply apparatus includesa pressure tank 3 and a discharge-side pressure sensor 4 at thedischarge side of the pumps 1, and flow switches (flow rate detectingmeans) 6 and check valves 7 for the respective pumps 1. A suction-sidepipe 8 of the pumps 1 is connected to a water main 9. A suction-sidepressure sensor 10 and a backflow prevention device 11 are provided inthe suction-side pipe 8. Further, a bypass pipe 12 for supplying wateronly by the pressure of the water main 9 is provided between thesuction-side pipe 8 and a discharge-side pipe 13 for the pumps 1. Acheck valve 14 is provided in the middle of the bypass pipe 12. Acontroller 15 for controlling the pumps 1 controls the rotational speedsof the pumps 1 and the number of operating pumps 1 according to thesituation, based on signals from these sensors.

If the water supply apparatus is not a directly connected water supplyapparatus whose suction-side pipe of the pump is connected to the watermain, but is a receiving tank type water supply apparatus, then thesuction-side pipe of the pump is connected to a water receiving tank,and a water level detector provided in the water receiving tank isconnected to the controller. The receiving tank type water supplyapparatus is free of the backflow prevention device, the suction-sidepressure sensor, and the bypass pipe.

FIG. 2 shows a required head curve A representing the relationshipbetween a usage flow rate and a pump head required for the usage flowrate, and a standard control head curve B established based on therequired head curve A, as well as Q-H curves of the pump (rotationalspeeds N₁, N₂, N₃ of the pump). In FIG. 2, the horizontal axisrepresents the flow rate Q, and the vertical axis represents the pumphead (head) H.

The required head curve A is determined from the sum (H₁+H₂+H₃) of thehead H₁ of, for example, the building (the height of the highest floorof the building), the pressure H₂ required for the water supplyinstrument (pressure loss caused by the water supply instrument), andthe piping loss H₃ depending on the flow rate. In the illustratedexample, the required head curve A is plotted as a curve smoothlyinterconnecting a head PB₀ required when the usage flow rate is nil anda head PA₀ required when the usage flow rate is of a final point Q₀.

The required head curve A is determined from the relationship between anideal pump head and a usage flow rate. For actual designs, it has widelybeen customary to establish the standard control head curve B which ishigher than the required head curve A by a margin of, e.g. a dozen %,and to control the rotational speed of the pump based on the standardcontrol head curve B. The standard control head curve B is plotted as acurve smoothly interconnecting a head (lowest required pressure) PB₁,which is higher than the head PB₀ by a margin of a dozen %, requiredwhen the usage flow rate is nil, and a head (highest required pressure)PA₁, which is higher than the head PA₀ by a margin of a dozen %,required when the usage flow rate is of the final point Q₀.

The standard control head curve B is stored in a memory of thecontroller 15 of the water supply apparatus shown in FIG. 1. Based onthe standard control head curve B, the controller 15 controls therotational speed of the pump 1 so that when the usage flow rate is Q₁,the intersection U₃ between the flow rate Q₁ and the standard controlhead curve B will be at the operating point (rotational speed N₁) of thepump 1, as shown in FIG. 2, for example.

In this manner, the standard control head curve B which is higher thanthe required head curve A by a margin of a dozen % is set, and therotational speed of the pump is controlled based on the standard controlhead curve B. Therefore, for example, in the case where the water pipeis corroded, causing a greater piping loss than the initially designedpiping loss, the water supply apparatus is prevented from failing toexercise the required performance in use and is able to meet the demandfor an increase in the flow rate that the user may want to achieve forsome reason.

There has been proposed a method of inputting a flow rate determinedfrom the pipe resistance and the pump performance curve andautomatically controlling the rotational speed of the pump in order toachieve the desired flow rate (see Patent document 1). According to theproposed method, when the flow rate is initially measured, if the flowrate is high, then the rotational speed of the pump is automaticallylowered. If the flow rate is still high regardless of the reduction inthe rotational speed of the pump, then the rotational speed of the pumpis further automatically lowered so as to meet the flow rate. In thismanner, the rotational speed of the pump is automatically adjustedsequentially until a target flow rate is reached.

CITATION LIST Patent Literature

-   Patent document 1: Japanese laid-open patent publication No.    59-51193

SUMMARY OF INVENTION Technical Problem

However, when the standard control head curve B which is higher than therequired head curve A by a margin of a dozen % is set, and therotational speed of the pump is controlled based only on the standardcontrol head curve B, no flexible solution has been found to meetenergy-saving demands. For example, as shown in FIG. 2, when therotational speed of the pump is controlled based only on the standardcontrol head curve B to achieve the flow rate Q₁ required by the user,the rotational speed of the pump is adjusted to N₁ so that theintersection U₃ between the flow rate Q₁ and the standard control headcurve B will be at the operating point. Therefore, the operating pointcannot be changed as required.

However, if the flow rate Q₁ required by the user is ensured, then thereare instances where the rotational speed of the pump may be adjusted toN₂ so that the intersection U₂, whose head is higher than the head atthe intersection (rotational speed N₃) U₁ between the flow rate Q₁ andthe required head curve A and lower than the head at the intersectionU₃, as shown in FIG. 2, will be at the operating point. In such a case,if the pump is operated at the intersection U₃ whose head is higher, therotational speed of the pump is higher compared to the case where thepump is operated at the intersection U₂ whose head is lower, and hencethe pump consumes more electric power. Such a mode of operation goesagainst today's stricter needs for energy saving.

Occasionally, the user may find it unnecessary to control the rotationalspeed of the pump based on the standard control head curve which has asufficient margin. In such a case, demands for energy saving can be metby controlling the rotational speed of the pump based on a control headcurve which has a minimum margin required.

However, the invention disclosed in Patent document 1 is not intended toachieve such energy saving.

The present invention has been made in view of the above circumstances.It is therefore an object of the present invention to provide a watersupply apparatus which is capable of controlling the rotational speed ofa pump so as to lower the rotational speed of the pump while keeping aconstant flow rate, thereby meeting demands for energy saving.

Solution to Problem

The present invention recited in claim 1 relates to a water supplyapparatus comprising: a pump configured to pressurize and deliver water;a frequency converter configured to supply electric power to the pump tooperate the pump at a desired rotational speed; a discharge-sidepressure sensor configured to detect a pressure at a discharge side ofthe pump; and a controller configured to control the rotational speed ofthe pump; wherein the controller stores a plurality of control headcurves representing different relationships between flow rates andheads, and controls the rotational speed of the pump based on analternatively selected one of the control head curves.

For example, a first control head curve and a second control head curvewhose pressure (head) is set to be lower than that of the first controlcurve are stored in the controller. Then, normally, the controllercontrols the rotational speed of the pump based on the first controlhead curve, and as required, the controller controls the rotationalspeed of the pump based on the second control head curve. Thus, thewater supply apparatus can save more energy by operating the pump at alower rotational speed while maintaining the usage flow rate of water,compared to the case where the rotational speed of the pump iscontrolled based only on the first control head curve.

The present invention recited in claim 2 relates to the water supplyapparatus according to claim 1 which further comprises an operationpanel having a selector button configured to successively switch theplural control head curves stored in the controller and an energy-savingindicator configured to indicate energy-saving levels corresponding tothe control head curves used to control the rotational speed of thepump.

Therefore, the user of the water supply apparatus can easily select oneof the control head curves used for control by using the selectorbutton, and can confirm the selected state on the energy-savingindicator.

The present invention recited in claim 3 relates to the water supplyapparatus according to claim 1 or 2, wherein the plural control headcurves include a standard control head curve and a small-flow-rate-rangeenergy-saving control head curve whose head is lower than that of thestandard control head curve in a small flow rate range.

The present invention recited in claim 4 relates to the water supplyapparatus according to claims 1 to 3, wherein the plural control headcurves include a standard control head curve and amedium-flow-rate-range energy-saving control head curve whose head islower than that of the standard control head curve in a medium flow raterange.

The present invention recited in claim 5 relates to the water supplyapparatus according to any one of claims 1 to 4, wherein the pluralcontrol head curves include a standard control head curve and alarge-flow-rate-range energy-saving control head curve whose head islower than that of the standard control head curve in a large flow raterange.

The present invention recited in claim 6 relates to the water supplyapparatus according to any one of claims 1 to 5, wherein the pluralcontrol head curves include a standard control head curve and afull-flow-rate-range energy-saving control head curve which extendssubstantially parallel to the standard control head curve and whose headis lower than that of the standard control head curve in a full flowrate range.

Advantageous Effects of Invention

According to the water supply apparatus of the present invention, evenif the usage flow rate remains the same, the pump can be operated at anoperating point having a lower rotational speed, as required.Consequently, the amount of electric power consumed for the water supplycan be reduced to achieve energy saving, leading to CO₂ reduction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing a structural example of a conventional watersupply apparatus;

FIG. 2 is a graph showing a required head curve of a water supplyapparatus, a standard control head curve of a conventional water supplyapparatus, and Q-H curves of a pump;

FIG. 3 is a view showing a structural example of a water supplyapparatus according to an embodiment of the present invention;

FIG. 4 is a graph showing a plurality of control head curves as well asa required head curve which are stored in a controller of the watersupply apparatus according to the embodiment of the present invention;

FIG. 5 is a plan view of an operation panel provided in the water supplyapparatus according to the embodiment of the present invention;

FIG. 6 is a graph showing a full-flow-rate-range energy-saving controlhead curve for use as a control head curve according to the presentinvention, as well as a required head curve and a standard control headcurve;

FIG. 7 is a graph showing a medium-flow-rate-range energy-saving controlhead curve for use as a control head curve according to the presentinvention, as well as a required head curve and a standard control headcurve;

FIG. 8 is a graph showing a large-flow-rate-range energy-saving controlhead curve for use as a control head curve according to the presentinvention, as well as a required head curve and a standard control headcurve;

FIG. 9 is a graph showing a small-flow-rate-range energy-saving controlhead curve for use as a control head curve according to the presentinvention, as well as a required head curve and a standard control headcurve; and

FIG. 10 is a graph showing the relationship between an amount ofsupplied water (flow rate) and time when the water supply apparatusoperates throughout the day.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described in detail belowwith reference to FIGS. 3 through 5. In FIGS. 1 through 5, identical orcorresponding parts are denoted by identical reference numerals, andwill not be described in duplication.

FIG. 3 is a view showing a structural example of a water supplyapparatus according to an embodiment of the present invention. As shownin FIG. 3, the water supply apparatus includes a controller 15 having asetting unit 16, a memory 17, a processor 18, a display unit 19, and anI/O unit 20. The setting unit 16 and the display unit 19 areincorporated in an operation panel 21 of the water supply apparatus.Details of the parts other than the controller 15 are essentially thesame as those of the conventional water supply apparatus shown in FIG.1.

The setting unit 16 is used to establish various settings such as aplurality of control head curves, etc. which represent the differentrelationships between flow rates and heads, by external operation. Thevarious settings such as a plurality of control head curves, etc. thatare established by the setting unit 16 are stored in the memory 17. Forexample, the above-mentioned head (lowest required pressure) PB₁required when the usage flow rate is nil, and the above-mentioned head(highest required pressure) PA₁ required when the usage flow rate is ofthe final point Q₀, are inputted as settings to the memory 17 and storedtherein. The I/O unit 20 receives signals from various sensors installedin the water supply apparatus, such as an output signal from thedischarge-side pressure sensor 4 and a signal from the flow switch 6,and sends the received signals to the processor 18. Further, the I/Ounit 20 and the inverters 2 are connected to each other by communicationmeans such as RS485. The controller 15 sends various settings, frequencycommand values, and control signals including start and stop signals tothe inverters 2, and the inverters 2 sequentially send operationaldetails including actual frequency values and current values to thecontroller 15.

FIG. 4 shows a plurality of control head curves established by thesetting unit 16 and stored in the memory 17. The illustrated exampleuses a required head curve A that is determined from the sum (H₁+H₂+H₃)of, for example, the head H₁ of the building (the height of the highestfloor of the building), the pressure H₂ required for the water supplyinstrument (the pressure loss caused by the water supply instrument),and the piping loss H₃ depending on the flow rate, and a total of fourcontrol head curves including a standard control head curve B which ishigher than the required head curve A by a margin of, e.g. a dozen %,and three full-flow-rate-range energy-saving control head curves C₁, C₂,C₃.

The full-flow-rate-range energy-saving control head curves C₁, C₂, C₃extend substantially parallel to the standard control head curve B andhave heads lower than that of the standard control head curve B andhigher than that of the required head curve A over the full flow raterange. The heads of the full-flow-rate-range energy-saving control headcurves C₁, C₂, C₃ are successively lower in the order named. Then, oneof the four control head curves B, C₁, C₂, C₃ is selected, and therotational speed of the pump 1 is controlled based on the selected oneof the four control head curves B, C₁, C₂, C₃.

FIG. 5 is a plan view of the operation panel 21 of the water supplyapparatus. As shown in FIG. 5, the operation panel 21 has a selectorbutton 22 for successively selecting the four control head curves B, C₁,C₂, C₃ that are stored in the controller 17, and an energy-savingindicator 23 for indicating energy-saving levels corresponding to thecontrol head curves that are used to control the rotational speed of thepump 1.

When the selector button 22 is not pressed, any lamps of theenergy-saving indicator 23 are not turned on, and the standard controlhead curve B is used to control the rotational speed of the pump 1. Whenthe selector button 22 is pressed once, a lamp corresponding to “L” onthe energy-saving indicator 23 is turned on, and thefull-flow-rate-range energy-saving control head curve C₁ is used tocontrol the rotational speed of the pump 1. When the selector button 22is pressed twice, a lamp corresponding to “M” on the energy-savingindicator 23 is turned on, and the full-flow-rate-range energy-savingcontrol head curve C₂ is used to control the rotational speed of thepump 1. Further, when the selector button 22 is pressed three times, alamp corresponding to “H” on the energy-saving indicator 23 is turnedon, and the full-flow-rate-range energy-saving control head curve C₃ isused to control the rotational speed of the pump 1. When the selectorbutton 22 is pressed four times, the energy-saving indicator 23 goesback to the original state.

Therefore, the user can easily select one of the control head curves B,C₁, C₂, C₃ used for control by pressing the selector button 22, and canconfirm the selected state on the energy-saving indicator 23.

Operation of the water supply apparatus for controlling the rotationalspeed of the pump to achieve the flow rate Q₁ required by the user willbe described below with reference to FIG. 4. First, when the user doesnot press the selector button 22, the rotational speed of the pump 1 iscontrolled based on the standard control head curve B, so that theintersection U₃ between the standard control head curve B and the flowrate Q₁ will be at the operating point of the pump 1. At this time, anylamps of the energy-saving indicator 23 are not turned on.

When the user presses the selector button 22 once, the rotational speedof the pump 1 is controlled based on the full-flow-rate-rangeenergy-saving control head curve C₁, so that the intersection U₄ betweenthe full-flow-rate-range energy-saving control head curve C₁ and theflow rate Q₁ will be at the operating point of the pump 1. At this time,the lamp corresponding to “L” on the energy-saving indicator 23 isturned on. When the user presses the selector button 22 twice, therotational speed of the pump 1 is controlled based on thefull-flow-rate-range energy-saving control head curve C₂, so that theintersection U₅ between the full-flow-rate-range energy-saving controlhead curve C₂ and the flow rate Q₁ will be at the operating point of thepump 1. At this time, the lamp corresponding to “M” on the energy-savingindicator 23 is turned on. Then, when the user presses the selectorbutton 22 three times, the rotational speed of the pump 1 is controlledbased on the full-flow-rate-range energy-saving control head curve C₃,so that the intersection U₆ between the full-flow-rate-rangeenergy-saving control head curve C₃ and the flow rate Q₁ will be at theoperating point of the pump 1. At this time, the lamp corresponding to“H” on the energy-saving indicator 23 is turned on.

In this manner, even if the usage flow rate remains the same, the pump 1can be operated at a selected operating point having a lower rotationalspeed, as required. Consequently, the amount of electric power consumedfor the water supply can be reduced to achieve energy saving, leading toCO₂ reduction.

In the above example, as shown in FIG. 6, a plurality of (three in theexample) full-flow-rate-range energy-saving control head curves C thatextend substantially parallel to the standard control head curve B andhave heads lower than that of the standard control head curve B andhigher than that of the required head curve A over the full flow raterange are used to achieve a substantially constant level of energysaving over the full flow rate range.

As shown in FIG. 7, a medium-flow-rate range energy-saving control headcurve D that has a head lower than that of the standard control headcurve B in a medium flow rate range may be used to achieve energy savingprimarily in the medium flow rate range. In this case, a plurality ofmedium-flow-rate range energy-saving control head curves D havingrespective heads different from the standard control head curve B in themedium flow rate range may be used to achieve stepwise energy saving.

Further, as shown in FIG. 8, a large-flow-rate range energy-savingcontrol head curve E that has a head lower than that of the standardcontrol head curve B in a large flow rate range may be used to achieveenergy saving primarily in the large flow rate range. In this case, aplurality of large-flow-rate range energy-saving control head curves Ehaving respective heads different from the standard control head curve Bin the large flow rate range may be used to achieve stepwise energysaving.

Furthermore, as shown in FIG. 9, a small-flow-rate range energy-savingcontrol head curve F that has a head lower than that of the standardcontrol head curve B in a small flow rate range may be used to achieveenergy saving primarily in the small flow rate range. In this case, aplurality of small-flow-rate range energy-saving control head curves Fhaving respective heads different from the standard control head curve Bin the small flow rate range may be used to achieve stepwise energysaving.

The full-flow-rate-range energy-saving control head curve C shown inFIG. 6, the medium-flow-rate range energy-saving control head curve Dshown in FIG. 7, the large-flow-rate range energy-saving control headcurve E shown in FIG. 8, and the small-flow-rate range energy-savingcontrol head curve F shown in FIG. 9 may be combined in any desiredcombinations to control the rotational speed of the pump, therebyachieving a desired flow rate and a desired head while maintaining anenergy-saving effect.

The water supply apparatus was operated throughout the day to supplywater at hourly rates (flow rates) kept as shown in FIG. 10 under a head(water supply pressure) of 40 m and then 36 m. The relationship betweenhours, water supply ratios, amounts of supplied water, and amounts ofconsumed electric power (hourly consumed electric power) under the headof 36 m is shown in Table 1 below, and the relationship between hours,water supply ratios, amounts of supplied water, and amounts of consumedelectric power (hourly consumed electric power) under the head of 40 mis shown in Table 2 below.

TABLE 1 Water Amount of supply Amount of supplied consumed electric Hourratio % water L/min power kWh 0~1 30 8.3 0.51 1~2 10 2.8 0.50 2~3 10 2.80.50 3~4 10 2.8 0.50 4~5 12 3.3 0.50 5~6 41 11.4 0.52 6~7 85 23.6 0.567~8 138 38.3 0.62 8~9 247 68.6 0.77  9~10 215 59.7 0.72 10~11 164 45.60.65 11~12 124 34.4 0.60 12~13 114 31.7 0.59 13~14 95 26.4 0.57 14~15 9526.4 0.57 15~16 96 26.7 0.57 16~17 110 30.6 0.59 17~18 125 34.7 0.6018~19 153 42.5 0.64 19~20 143 39.7 0.62 20~21 129 35.8 0.61 21~22 11130.8 0.59 22~23 88 24.4 0.56 23~24 55 15.3 0.53 Hourly-averaged 100 27.8Total 13.99 amount of supplied water

The water supply ratio represents an hourly ratio with respect to thehourly-averaged amount of supplied water which is 100.

TABLE 2 Water Amount of supply Amount of supplied consumed electric Hourratio % water L/min power kWh 0~1 30 8.3 0.60 1~2 10 2.8 0.59 2~3 10 2.80.59 3~4 10 2.8 0.59 4~5 12 3.3 0.59 5~6 41 11.4 0.61 6~7 85 23.6 0.667~8 138 38.3 0.72 8~9 247 68.6 0.90  9~10 215 59.7 0.84 10~11 164 45.60.76 11~12 124 34.4 0.70 12~13 114 31.7 0.69 13~14 95 26.4 0.67 14~15 9526.4 0.67 15~16 96 26.7 0.67 16~17 110 30.6 0.69 17~18 125 34.7 0.7118~19 153 42.5 0.74 19~20 143 39.7 0.73 20~21 129 35.8 0.71 21~22 11130.8 0.69 22~23 88 24.4 0.66 23~24 55 15.3 0.63 Hourly-averaged 100 27.8Total 16.41 amount of supplied water

The water supply ratio represents an hourly ratio with respect to thehourly-averaged amount of supplied water which is 100.

It will be seen from Table 1 and Table 2 that when the water supplyapparatus operates throughout the day to supply water under a head(water supply pressure) reduced from 40 m to 36 m, the total amount ofconsumed electric power is reduced from 16.41 kWh to 13.99 kWh.Therefore, the amount of saved energy per day is 2.42 kWh, and theamount of saved energy per year is 883 kWh, which is converted into 358kg of CO₂ (CO₂ conversion coefficient recommended by Tokyo ElectricPower Company, Incorporated: 1 kWh=0.43 kg). Since one cedar tree canabsorb 14.5 kg of CO₂ per year (because 11000 cedar trees absorb 160 tof CO₂ per year according to Workshop of Iron Nutrition Enhancement inPlants), CO₂ reduction equivalent to about 25 cedar trees can beachieved.

A plurality of control head curves may be used, and when the user feelsthat the head is low, the user may select one of the control head curveswhich has a higher head. Specifically, according to the aboveembodiment, the standard control head curve B and several control headcurves whose heads are lower than that of the standard control headcurve B fully or partly over the flow rate range thereof are stored inthe controller, and one of the several control head curves is selected.However, the standard control head curve B and several control headcurves whose heads are higher than that of the standard control headcurve B fully or partly over the flow rate range thereof may be storedin the controller, and one of the several control head curves may beselected.

Although the embodiment of present invention has been described above,the present invention is not limited to the above embodiment, but may bereduced to practice in various different manners within the scope of thetechnical concept thereof. The water supply apparatus according to thepresent invention allows the user to select one of the control headcurves for the purpose of energy saving, i.e. for reducing the amount ofelectric power used to operate the pump. However, the present inventionis not limited to such purpose, but is also applicable to a water supplyapparatus which allows the user to select one of control head curves forthe purpose of saving water.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a water supply apparatus forsupplying water such as tap water to collective housing or a buildingusing a pump.

REFERENCE SIGNS LIST

-   -   1 pump    -   2 inverter (frequency converter)    -   3 pressure tank    -   4 discharge-side pressure sensor    -   8 suction-side pipe    -   9 water main    -   10 suction-side pressure sensor    -   12 bypass pipe    -   13 discharge-side pipe    -   15 controller    -   16 setting unit    -   17 memory    -   18 processor    -   19 display unit    -   20 I/O unit    -   21 operation panel    -   22 selector button    -   23 energy-saving indicator    -   A required head curve    -   B standard control head curve    -   C full-flow-rate-range energy-saving control head curve    -   D medium-flow-rate-range energy-saving control head curve    -   E large-flow-rate-range energy-saving control head curve    -   F small-flow-rate-range energy-saving control head curve

1. A water supply apparatus comprising: a pump configured to pressurizeand deliver water; a frequency converter configured to supply electricpower to the pump to operate the pump at a desired rotational speed; adischarge-side pressure sensor configured to detect a pressure at adischarge side of the pump; and a controller configured to control therotational speed of the pump; wherein the controller stores a pluralityof control head curves representing different relationships between flowrates and heads, and controls the rotational speed of the pump based onan alternatively selected one of the control head curves.
 2. A watersupply apparatus according to claim 1, further comprising: an operationpanel having a selector button configured to successively switch theplural control head curves stored in the controller and an energy-savingindicator configured to indicate energy-saving levels corresponding tothe control head curves used to control the rotational speed of thepump.
 3. A water supply apparatus according to claim 1, wherein theplural control head curves include a standard control head curve and asmall-flow-rate-range energy-saving control head curve whose head islower than that of the standard control head curve in a small flow raterange.
 4. A water supply apparatus according to claim 1, wherein theplural control head curves include a standard control head curve and amedium-flow-rate-range energy-saving control head curve whose head islower than that of the standard control head curve in a medium flow raterange.
 5. A water supply apparatus according to claim 1, wherein theplural control head curves include a standard control head curve and alarge-flow-rate-range energy-saving control head curve whose head islower than that of the standard control head curve in a large flow raterange.
 6. A water supply apparatus according to claim 1, wherein theplural control head curves include a standard control head curve and afull-flow-rate-range energy-saving control head curve which extendssubstantially parallel to the standard control head curve and whose headis lower than that of the standard control head curve in a full flowrate range.
 7. A water supply apparatus according to claim 2, whereinthe plural control head curves include a standard control head curve anda small-flow-rate-range energy-saving control head curve whose head islower than that of the standard control head curve in a small flow raterange.
 8. A water supply apparatus according to claim 2, wherein theplural control head curves include a standard control head curve and amedium-flow-rate-range energy-saving control head curve whose head islower than that of the standard control head curve in a medium flow raterange.
 9. A water supply apparatus according to claim 2, wherein theplural control head curves include a standard control head curve and alarge-flow-rate-range energy-saving control head curve whose head islower than that of the standard control head curve in a large flow raterange.
 10. A water supply apparatus according to claim 2, wherein theplural control head curves include a standard control head curve and afull-flow-rate-range energy-saving control head curve which extendssubstantially parallel to the standard control head curve and whose headis lower than that of the standard control head curve in a full flowrate range.
 11. A water supply apparatus according to claim 3, whereinthe plural control head curves include a medium-flow-rate-rangeenergy-saving control head curve whose head is lower than that of thestandard control head curve in a medium flow rate range.
 12. A watersupply apparatus according to claim 3, wherein the plural control headcurves include a large-flow-rate-range energy-saving control head curvewhose head is lower than that of the standard control head curve in alarge flow rate range.
 13. A water supply apparatus according to claim3, wherein the plural control head curves include a full-flow-rate-rangeenergy-saving control head curve which extends substantially parallel tothe standard control head curve and whose head is lower than that of thestandard control head curve in a full flow rate range.
 14. A watersupply apparatus according to claim 4, wherein the plural control headcurves include a large-flow-rate-range energy-saving control head curvewhose head is lower than that of the standard control head curve in alarge flow rate range.
 15. A water supply apparatus according to claim4, wherein the plural control head curves include a full-flow-rate-rangeenergy-saving control head curve which extends substantially parallel tothe standard control head curve and whose head is lower than that of thestandard control head curve in a full flow rate range.
 16. A watersupply apparatus according to claim 5, wherein the plural control headcurves include a full-flow-rate-range energy-saving control head curvewhich extends substantially parallel to the standard control head curveand whose head is lower than that of the standard control head curve ina full flow rate range.